<!-- 城市选择右侧字母选择插件 -->
<template>
    <ul class="list">
        <li class="item" 
            v-for="item in letters" 
            :key="item" 
            :ref="item"
            @click="handleClick" 
            @touchstart.prevent="handleTouch" 
            @touchmove="handleMove"
            @touchend="handleEnd"
        >{{item}}</li>
    </ul>
</template>

<script>
export default {
  name: "CityAlphabet",
  props: ["cities"],
  data() {
    return {
      touchStatus: false,
      startY: 0,
      timer: null
    };
  },
  updated() {
    this.startY = this.$refs["A"][0].offsetTop; // 'A' 距离顶部的位置
  },
  computed: {
    letters() {
      const letters = [];
      for (let i in this.cities) {
        letters.push(i);
      }
      return letters;
    }
  },
  methods: {
    handleClick(e) {
      //   console.log(e.target.innerText);
      this.$emit("change", e.target.innerText);
    },
    handleTouch() {
      this.touchStatus = true;
    },
    handleMove(e) {
      if (this.touchStatus) {
        if (this.timer) {
          clearTimeout(this.timer);
        }
        this.timer = setTimeout(() => {
          const touchY = e.touches[0].clientY - 79;
          const index = Math.floor((touchY - this.startY) / 20);
          console.log(index);
          if (index >= 0 && index < this.letters.length) {
            this.$emit("change", this.letters[index]);
          }
        }, 16);
      }
    },
    handleEnd() {
      this.touchStatus = false;
    }
  }
};
</script>

<style lang="stylus" scoped>
@import '~styles/varibles.styl'
@import '~styles/mixins.styl'
.list
    display flex
    flex-direction column
    justify-content center
    text-align center
    position absolute
    top 1.58rem
    right 0
    bottom 0
    width 0.4rem
    .item
        line-height 0.4rem
        color $bgColor
</style>

